PEST RISK ANALYSIS (PRA) TRAINING Group Exercises Manual

APPENDIX 8
PEST RISK ANALYSIS TRAINING - GROUP EXERCISES MANUAL
Grove et al.: Thrips species associated with mango trees in South Africa 157
Table 2. Thrips species collected at weekly intervals from mango flowers in a open-pollinated seedling orchard at
Nelspruit.
Date
Status of flowers/fruit
Species (number collected)
1995-08-14 H. gowdeyi (2). Haplothrips sp. (2), S. aurantii (24), larvae (3)
All flowers on panicle closed
1995-08-2 1 H. gowdeyi (14), S. aurantii (1), larvae (1)
15 % of flowers on panicle open
1995-08-28 H. clarisetis (10), F schultzei (6), S. aurantii (14), T. tenellus (5)
85 % of flowers on panicle open larvae (2)
1995-09-04 H. gowdeyi (2), S. aurantii (14), T. tenellus (4)
100 % of flowers on panicle open
1995-09-11 S. aurantii (10), T. tenellus (8), larvae (15)
Small fruit setting
1995-09-18 H. bedfordi (2), H. gowdeyi (2), S. aurantii (14), T. tenellus (4)
Average fruit length 3 mm
1995-09-26 S. aurantii (18), larvae (3)
Average fruit length 9 mm
1995-10-02 S. aurantii (34), larvae (12)
Average fruit length 12 mm
1995-10-09 S. aurantii (20), larvae (16)
Average fruit length 22 mm
1995-10-16 S. aurantii (1)
Average fruit length 39 mm
1995-10-23 S. aurantii (1), larvae (1)
Average fruit length 58 mm
1995-10-30 -
Average fruit length 58 mm
1995-11-06 -
Average fruit length 71 mm
Fungal diseases are present on mangoes in South
Africa (Manicom 1998), but thrips are not
considered to be particularly important as vectors
of pathogens relative to dissemination occurring
by wind and rain (Ullman et al. 1997)
Monitoring thrips in the flowers and on young
fruit
Scirtothrips aurantii was the most abundant
species found in the flowers and on young fruit in
the open-pollinated seedling orchard at Nelspruit
(Table 2). Haplothrips gowdeyi and T. tenellus
were also found in high numbers during the
flowering period. Scirtothrips aurantii was the
only species found on the fruit as it developed
beyond 9 mm. This was the only orchard where S.
aurantii was found in such high numbers in the
flowers. The orchard consisted of different
selected seedlings and the population probably
built up on the fruit and flowers of the early
selections. By the time that most trees started to
flower, S. aurantii was already present in high
numbers. Therefore S. aurantii can be present in
high numbers in the flowers, although numbers
usually build upon small fruit.
In contrast to the Nelspruit orchard, T. acaciae
was the most abundant species in the Zill and
Sensation orchard at the ITSC Friedenheim
Experimental Farm during 1996 (Tables 3, 4),
while S. aurantii was absent. Thrips tenellus was
also present in fairly high numbers in the Zill and
Sensation orchard at Friedenheim.
Monitoring thrips with yellow card traps
Yellow sticky card traps were an effective
method for monitoring thrips species and
numbers. The traps were easy to use and handle.
The thrips trapped were mainly S. aurantii and T.
tenellus, while other species with very low
abundance were omitted. Thrips acaciae was
abundant at Friedenheim during 1996 and was
thus included. The abundance of T. tenellus and S.
aurantii in the Sensation orchard at Nelspruit
during 1992/93 is illustrated in Fig. 1. The
numbers of T. tenellus were high during the
flowering period, but declined
84